Paul Walker was previously attached to play the lead role in this film before his sudden death in late November, 2013.
There is a direct reference to the video game franchise made in one brief scene where a yellow rubber duck is seen floating in a bathtub along with a partially submerged toaster.
The pose Agent 47 makes while exiting an elevator early in the film by facing forward and crossing his arm over his chest while holding his pistol is reminiscent of signature promotional images used throughout the Hitman video game franchise but the "blood on the sleeve" is from a cover of Hitman: Absolution.
Seen in the trailer is Agent 47 wearing the uniform of a dispatched police officer as a disguise to aid his escape, a staple of the Hitman games.
In the month's prior to the movie's release, 20th Century Fox and IGN Entertainment launched a social media campaign in order to find Hitman Agents 1 through 46. Contest entries, which were mostly comprised Agent 47 cosplay photos, were judged by a panel and winners were officially given numeric designations in the Hitman canon.
The idea of a young girl who has assassin-like abilities (like super reflexes and freeing herself from her ties) who is also wanted by an evil corporation is taken directly from the plot of Hitman: Absolution (2012).
Rupert Friend accidentally hurt himself while firing a blank bullet for one scene. The hot shell bounced off the floor, and hit him in the head, burning him slightly.
During a series of quick cuts, a man can be seen holding a Sony PlayStation video game controller. Most of the early Hitman games were available on the PlayStation 2 system.
At 20:30 Hitman picks up Katie's prescription bottle. We see she's taking Dilantin which is an anticonvulsant that can treat and prevent seizures.